Follow US immigration and follow US technology development: A new research report from the United States shows that the currently observed changes in global precipitation cannot be explained solely by natural climate fluctuations, and that human activity has directly affected global precipitation.
Researchers at the Lawrence Livermore National Laboratory in the United States reported in the latest online issue of the Proceedings of the National Academy of Sciences that greenhouse gases and ozone-depleting gases emitted by human activities affect global precipitation through two mechanisms: on one hand, climate warming causes wet regions to become wetter and dry regions to become drier; on the other hand, changes in atmospheric circulation patterns push storm tracks and subtropical dry zones toward the Earth's poles.
In addition, after comparing climate models with observations from the US "Global Precipitation Climatology Project" between 1979 and 2012, researchers found that while natural climate fluctuations (such as El Niño and La Niña) can lead to extreme precipitation or the shifting of precipitation toward the Earth's poles, these two phenomena rarely occur simultaneously under natural conditions.
The study's lead author, Kate Marvel, said: "The simultaneous occurrence of extreme precipitation and the shift of precipitation toward the Earth's poles cannot be explained by natural fluctuations alone. Previous work has mostly studied one of these two changes in isolation, but by studying them together, we have discovered a pattern of precipitation change influenced by human activity."
Researcher Céline Bonfils stated that, taken together, "the increase in greenhouse gases and ozone layer depletion caused by human activities should be the cause of global precipitation changes," and the simultaneous appearance of extreme precipitation and the shift of precipitation toward the Earth's poles "is strong evidence of human activity affecting global precipitation."